1. Field of the Invention
The invention relates to electrodeless lamps excited by radio frequency (RF) fields.
2. Description of the Prior Art
Numerous patents disclose electrodeless bulbs which are excited by RF energy using an electrically conductive coupler having one or more turns of an electrical conductor wrapped around the outside of the bulb. See U.S. Pat. Nos. 4,204,834, 4,792,725, 5,063,333, 5,070,277, 5,072,157, 5,130,612, 5,280,217, 5,306,987, 5,886,478, 5,923,116, 5,990,632, 6,046,545, 6,107,752, 6,137,237, 6,145,979, 6,248,805 and 6,249,090. Depending upon the design of the RF excitation system, the one or more turns of the electrically conductive coupler which excites the bulb operate based upon the principle of inductive and/or capacitive coupling to the electrodeless bulb.
Electrodeless lamp assemblies which are excited by an electrically conductive coupler having one or more turns of an electrical conductor wrapped around the bulb are highly advantageous in view of their ability to generate substantial light output in either the visible or ultra-violet (UV) range within a compact housing. However, a compact housing exacerbates cooling of the bulb and the one or more turns of the electrically conductive coupler which are in a fixed relationship to the bulb. Moreover, prevention of coupling of RF energy from the electrically conductive coupler through stray capacitance or inductance to the housing containing the electrodeless bulb is desirable to produce the maximum amount of optical output with the smallest input of RF power.
Furthermore, in applications utilizing a compact UV light generator, such as to reproduce photographs which are digitally stored, low operating temperature of outer walls of the housing of the UV lamp assembly is highly desirable. In most applications requiring a compact light source, the light source is a component in a larger machine. Thus, compactness and low operating temperature on the lamp surfaces are valuable because it allows the larger machine components to be made from inexpensive temperature sensitive materials, such as plastic, and further allows the components to be mounted in close proximity to the UV lamp contributing to the efficiency of the overall design.
The present invention provides a compact electrodeless lamp assembly which has high output in a selected part of the spectrum which is useful for diverse applications. The outer wall of the compact housing is maintained at a temperature during operation which will not burn.
The present invention further provides an optically reflective housing containing an electrodeless bulb which has minimal absorption of the light produced therein.
A lamp assembly in accordance with the invention utilizes an electrically conductive coupler which excites an electrodeless bulb comprising a plurality of turns which define a volume that at least partially contains the electrodeless bulb. A conductor is connected to a center portion of the electrically conductive coupler which fixes the coupler relative to the bulb.
The electrically conductive coupler provides a high efficiency coupling of the RF electrical field to the electrodeless bulb. The connection of the conductor to a center portion of the electrical coupler produces a symmetrical transfer of electrical power from the RF electrical field to the electrodeless bulb which ensures that power is dissipated uniformly in the electrodeless bulb which enhances efficiency and the life of the electrodeless bulb.
A lamp assembly in accordance with the invention includes an electrodeless bulb which is symmetrical about an axis and which contains a light emissive fill which emits light when the bulb is excited by a radio frequency electrical field coupled to the fill; an electrically conductive coupler comprising a plurality of turns which are symmetrical about an axis of the coupler, the turns defining a volume that at least partially contains the bulb; and a conductor connected to a center portion of the electrically conductive coupler with the connection of the conductor to the coupler providing a fixing of the coupler relative to the bulb which, when the conductor is connected to a source of radio frequency electrical potential, conducts a radio frequency current producing a radio frequency electrical potential on the electrically conductive coupler that produces the radio frequency electrical field coupled to the fill. The outer surface of the bulb may include a cylindrical section and the volume may include a cylindrical section. The axes may be substantially parallel and/or proximate to teach other. The conductor may be connected to one of the turns at a center portion of the electrically conductive coupler relative to ends thereof. Radio frequency power may be coupled symmetrically, relative to the center portion of electrically conductive coupler, to the fill. The plurality of turns may be a wire with a polygonal cross section which may be a triangle, a quadrilateral such as a square, or an equilateral polygon with more than four sides.
A lamp assembly in accordance with the invention includes an electrodeless bulb having an outer surface which is symmetrical about an axis and which contains a light emissive fill that emits light when the bulb is excited by a radio frequency electrical field coupled to the fill, an electrically conductive coupler comprising a plurality of turns which are symmetrical about an axis of the coupler, the turns defining a volume that at least partially contains the bulb, a conductor connected to a center portion of the electrically conductive coupler with the connecting of the conductor to the electrically conductive coupler providing a fixing of the coupler relative to the bulb which, when the conductor is connected to a source of radio frequency electrical potential, conducts a radio frequency current producing a radio frequency electrical potential on the electrically conductive coupler to produce the radio frequency electrical field coupled to the fill; and a light reflective chamber which contains the bulb, the electrically conductive coupler and the conductor, the chamber including a center section which reflects light emitted from the bulb out of an opening in the chamber, a top section and a bottom section and each of the top and bottom sections reflecting light emitted from the bulb and reflected from another of the top and bottom sections. The top and bottom sections may each include curved light reflective indentations which receive an end of the bulb and are indented in an outward manner relative to the chamber so that surfaces of the indentations are spaced further apart than remaining surfaces of the top and bottom sections which are not indented and the curved indentations reflect light emitted from the bulb. The lamp assembly may further include a housing containing the chamber, and at least one fan located in one end of the housing which inducts air from one end of the housing and blows the inducted air into contact with outer surfaces of the sections of the chamber and inner surfaces of the housing and then outwardly from the housing and blows air into the chamber past the bulb and the electrical coil and outwardly from the opening in the chamber. The housing may have sections which are joined together to define the one end and may include another end which surrounds the opening of the chamber and each section may include at least one opening located remote from the one end from which air is blown outwardly by the fan after cooling the sections of the chamber and the housing. The housing may comprise plastic. A plurality of fans may be located at the one end of the housing. The conductor may be connected to one of the turns substantially at a center portion of the electrically conductive coupler relative to ends thereof. Radio frequency power may be coupled symmetrically, relative to the center portion of the electrically conductive coupler, to the fill. The plurality of turns may be a wire with a polygonal cross section which may be a triangle, a quadrilateral such as a square, or an equilateral polygon with more than four sides.
A lighting system in accordance with the invention includes a plurality of lamp assemblies which are connected together, each lamp assembly comprising an electrodeless bulb having an outer surface which is symmetrical about an axis and which contains a light emissive fill which emits light when the bulb is excited by a radio frequency electrical field coupled to the fill, an electrically conductive coupler comprising a plurality of turns which are symmetrical about an axis of the coupler, the turns defining a volume that at least partially contains the bulb, a conductor connected to a center portion of the electrically conductive coupler with the connecting of the conductor to the electrically conductive coupler providing a fixing of the coupler relative to the bulb which, when the conductor is connected to a source of radio frequency electrical potential, conducts a radio frequency current producing a radio frequency electrical potential on the electrically conductive coupler to produce the radio electrical frequency field coupled to the light emissive fill; and a light reflective chamber which contains the bulb, the electrically conductive coupler and the conductor, the chamber including a center section which reflects light emitted from the bulb out of an opening in the chamber, a top section and a bottom section and each of the top and bottom sections reflecting light emitted from the bulb and reflected from another of the top and bottom sections.